In a bowl, mix butter and flour by hand to get coarse crumbles. Add egg and mix thoroughly. Add sugar and almond flour and work with your hands into a ball. Cover with film and refrigerate one hour min.
Spread into an 8 to 9" tart pan (metal or porcelain). Prick the bottom with a fork generously, and refrigerate again while you do the next steps.
Preheat your oven to 350 deg F.
In a bowl mix softened butter with almond flour. Add sugar and cornstarch, mix again. Add eggs one by one and mix thoroughly. Pour into the mold and spread it out evenly with a spatula. It should be about 1/4″ below the sides of the dough.
Bake in the oven for 20 to 30 minutes until it has a nice golden color (it will cook faster in a metal pan than porcelain). Let it cool down completely.
In a saucepan, melt the fruit jelly on medium heat. Remove from the heat and add the blueberries, stirring gently and quickly so they don’t burst or cook. Spread onto the cooled tart. The jelly should help keep the fruit together.
Keep refrigerated until you serve. If using a metal tart pan with removable bottom, take the tart out of the pan just before serving. Otherwise, serve in the dish!